Fig. 1: Schematic experimental setup, modulation waveforms, and synthetic lattices.
a Schematic experimental setup of two coupled fiber loops. Blue and red arrows denote light circulation directions in short and long loops. PM: phase modulator; AWG: arbitrary wave generator; PD: photon detector; OC: optical coupler; VOC: variable optical coupler. b Schematic modulation waveforms in AWG to generate a moving barrier. The squared gate voltages (red) denote the modulation signals in a period T for initial and three successive steps. v and vg denote the barrier’s moving speed and the packet’s group velocity c A moving gauge-potential barrier with moving speed v = 1/3 in a discrete-time temporal lattice made of leftward (blue) and rightward (red) links towards the node (n, m). The phase modulations are (ϕu2, ϕv2) and (ϕu1, ϕv1) inside and outside the barrier, corresponding to a gauge-potential distribution of (φ2, A2) and (φ1, A1). The two moving boundaries are n − vm = n1,2, where v is moving speed, n1, n2 are initial positions of two boundaries and W = n2 − n1 is barrier width. A Bloch-wave packet (purple) is incident from the right side of barrier. d Schematic of the lattice and gauge-potential distribution in the moving frame (n’, m’) obtained through Galilean transformation from laboratory frame (n, m).
